Lmsys Fastchat vulnerabilities

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Published CVEs affecting Lmsys Fastchat: 3 record(s), with affected versions and fixes.

CVE-2026-85695 Critical · 9.4 CWE-306 Sep 4, 2026

FastChat Unauthenticated Worker Registration SSRF and Model Spoofing

FastChat contains an authentication bypass vulnerability in the /register_worker endpoint that allows unauthenticated attackers to register arbitrary worker addresses and perform server-side request forgery. Attackers can register malicious workers under victim model names to intercept user prompts, images, and responses, or probe internal network ports across the worker mesh.

CVE-2026-6608 Medium · 5.3 CWE-670 Apr 20, 2026

lm-sys fastchat Arena Side-by-Side View add_text control flow

A vulnerability was detected in lm-sys fastchat up to 0.2.36. Impacted is the function add_text of the component Arena Side-by-Side View Handler. The manipulation results in incorrect control flow. The attack can be launched remotely. The exploit is now public and may be used. The root cause was fixed in commit 34eca62 for gradio_block_arena_named.py, but three other files were missed.

CVE-2026-6607 Medium · 5.3 CWE-400 Apr 20, 2026

lm-sys fastchat Worker API Endpoint api_generate resource consumption

A security vulnerability has been detected in lm-sys fastchat up to 0.2.36. This issue affects the function api_generate of the component Worker API Endpoint. The manipulation leads to resource consumption. The attack can be initiated remotely. The exploit has been disclosed publicly and may be used. The identifier of the patch is c9e84b89c91d45191dc24466888de526fa04cf33. It is suggested to install a patch to address this issue. Commit ff66426 patched this issue in api_generate of base_model_worker.py and did miss other entry points.